MRAM Cell Phase-Controlled Anisotropy for Low-Current Switching
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Solution Overview
Problem
Current spin-transfer torque magnetoresistive random access memory (STT-MRAM) devices face challenges in scalability and require high current densities to switch magnetization due to limited thermal stability, necessitating enhanced perpendicular magnetic anisotropy (PMA) and efficient magnetization manipulation.
Innovation Solution
Incorporating a phase change material layer, such as a metal-insulator transition (MIT) material, which undergoes a phase transition to modulate the perpendicular magnetic anisotropy of the free layer, reducing the magnetic anisotropy energy barrier and enabling efficient magnetization switching with lower current densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spin-polarized current is used to modulate magnetic anisotropy in existing magnetoresistive memory devices, then magnetic orientation can be controlled, but the efficiency of resistance differential for data storage is limited
Solution Approach 1:
The patent changes the physical state of the ferroelectric material layer between paraelectric and ferroelectric phases through temperature control or electric field application. This phase change modifies the magnetic anisotropy energy and magnetization direction of the adjacent magnetic layer, enabling efficient and reliable data storage without requiring high current densities
Solution Approach 2:
The ferroelectric material layer serves as an intermediary between the electric field and the magnetic layer. It transduces electrical signals into magnetic anisotropy modulation through its phase transition, which then controls the magnetization direction of the magnetic layer, achieving efficient and reliable data storage operation
2Ease of operation
If conventional two-terminal magnetoresistive memory structure is used, then device simplicity is maintained, but control over magnetic anisotropy and magnetization direction is insufficient
Solution Approach 1:
The patent divides the memory cell into functionally distinct layers: a ferroelectric material layer for phase transition-based control and a magnetic layer for data storage. This segmentation allows independent optimization of each layer's function, achieving superior magnetic anisotropy control while maintaining reasonable device complexity
Solution Approach 2:
The memory cell employs a composite structure combining ferroelectric material with magnetic material layers. This composite approach leverages the unique properties of both materials - the ferroelectric phase transition capability and the magnetic anisotropy - to achieve enhanced control over magnetization direction without excessive structural complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The phase change material layer enhances switching efficiency between memory states, reduces programming current density, and offers potential for ultra-fast spintronic devices by modulating the magnetic anisotropy and interfacial strain, improving thermal stability and device reliability.
Implementation Method 1
inducing an insulator-to-conductor phase transition in the MIT material by applying a programming voltage pulse
Implementation Method 2
A resistance differential of a magnetic junction structure between different magnetization states of the free layer can be employed to store data within the magnetoresistive random access memory (MRAM) cell
Implementation Method 3
When the spin-polarized current flows through a free layer of a magnetic junction structure or a spin valve, the electrons in the spin-polarized current can transfer at least some of their angular momentum to the free layer, thereby producing a torque on the magnetization of the free layer
Data Source
AI summary
A magnetoresistive memory cell includes a first terminal electrode, a second terminal electrode, and a magnetoresistive layer stack located between the first terminal electrode and the second terminal electrode and including, from one side to another, a reference layer, a dielectric tunnel barrier layer, a free layer, and a material layer having two different states of lattice deformation which have different average in-plane lattice constants and which are configured to apply different in-plane stress. The material layer may be a metal-insulator transition (MIT) material layer that exhibits a phase transition between an insulator state and a metal state.